What are the responsibilities and expectations of TSC members?

In https://github.com/chapel-lang/TSC/issues/21#issuecomment-3457647376, @stonea pointed out that in addition to a list of criteria for potential applicants to the TSC, we should also have a list of responsibilities / expectations of TSC members. Here's a starting point off the top of my head:

* Will make a best effort to participate in TSC activities such as meetings, discussions, and votes
* Will strive to be guided by what they consider to be best for the Chapel language, project, the investment in it so far, and its success going forward
* Will seek out and share opportunities to improve the project and grow the community over time [added based on Engin's comment below]

Start with the discussion in issue 21, comment 3457647376, and inspect the TSC repository artifacts to find where member criteria are documented. Turn the proposed responsibilities and expectations into a clear list alongside those criteria. Done means the repository contains an agreed, accessible statement of TSC member responsibilities.

Written by the indexing model from the issue text.